Important: Use at own risk! New better solution, which will maybe added in the next SynoCommunity BitTorrent Sync release! What you need: A Synology DiskStationBitTorrent Sync Beta installed over SynoCommunity (https://synocommunity.com/)SSH must be activated (http://forum.synology.com/wiki/index.php/Enabling_the_Command_Line_Interface)A SSH client (Putty: http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html)Short explanation: We create a group, which member will be the btsync user. So you can easily give permissions over the DSM. What to do: Stop the btsync package.Connect with SSH to your Synology, login as root and use the admin password.Run this two commands: synogroup --add sc-btsync btsyncsynogroup --descset sc-btsync "SynoCommunity's BitTorrent Sync group"Start the btsync package.Now you can give permissions via Control Panel -> Group.